No matter what the prognosis, cancer diagnosis produces emotional distress. Women diagnosed with breast cancer report depression, uncertainty about their future, and unrealistic fears of cancer recurrence. Extensive evidence from the multi-disciplinary field of psychoneuroimmunology (PNI) has demonstrated that emotional distress impairs immune function. Therefore, the experience of cancer diagnosis and its' associated treatments may not only place the cancer patient at risk psychologically but may also place them at risk immunologically. We have shown that women diagnosed with breast cancer, of either an invasive or non-invasive form, have significant psychological distress that continues throughout and beyond cancer treatment. Moreover, these women exhibit a significant and concomitant reduction in natural killer cell activity (NKCA) as well as a dysregulation in cytokine production. These observations are especially important in that recent evidence from gene depleted animals has shown impaired natural killer (NK) cell and cytokine metastasis. Hence, impairments in these forms of immune function may lead to reductions in cancer control. As a whole, these observations suggest that cancer diagnosis and its' treatment produce psychological as well as immunological sequelae that negatively impact the cancer patient. Increasingly, individuals with cancer seek holistic approaches to cancer care. MBSR is a mind-body, behavioral-intervention that shows promise as a technique to self-manage the distress associated with adverse medical conditions. Recently, MBSR was shown to reduce symptoms of stress and mood disturbance in a heterogeneous group of cancer patients. In HIV infected individuals, we have shown MBSR to improve immune function. Thus, there is a strong rationale to evaluate MBSR as a means by which to improve cancer-related immune dysregulation and psychological distress. The purpose of this exploratory R21 project is to evaluate MBSR as a mind-body approach that will improve cancer associated immune dysregulation and psychological distress. Two hypotheses will be tested: 1) Women, undergoing treatment for breast cancer, who participate in the MBSR program will exhibit improvements in immune function compared to women, undergoing treatment for breast cancer, who do not participate in MBSR. 2) Women, undergoing treatment for breast cancer, who participate in the MBSR program will report decreased perceived stress and mood disturbance compared to women, undergoing treatment for breast cancer, who do not participate in MBSR. Women (N=96) diagnosed with early stage cancer who will be treated with breast conserving surgery, radiotherapy, and tamoxifen, will be enrolled and randomly assigned to an MBSR program or to a control group (usual care). Immune function (NKCA and cytokine production) and psychological distress (perceived stress and mood) will be assessed pre-MBSR, mid-MBSR, at the completion of MBSR, and 1 month following MBSR. Within and between group differences in outcome measures will be determined. In this manner MBSR will be evaluated as a PNI, mind body approach, to counter the negative psychological and immunological aftermath of cancer diagnosis and treatment. Such an approach has the potential to lead to not only better cancer control but also to a better quality of life for cancer.